GENERAL ORGANIZATION OF THE CONJUGAL TRANSFER GENES OF THE INCW PLASMID R388 AND INTERACTIONS BETWEEN R388 AND INCN AND INCP PLASMIDS

The complete conjugal transfer gene region of the IncW plasmid R388 has been cloned in multicopy vector plasmids and mapped to a contiguous 14.9-kilobase segment by insertion mutagenesis. The fertility of the cloned region could still be inhibited by a coresident IncP plasmid. The transfer region has been dissected into two regions, one involved in pilus synthesis and assembly (PIL(W)), and the other involved in conjugal DNA metabolism (MOB(W). They have been separately cloned. PIL (W) also contains the genes involved in entry exclusion. MOB(W) contains oriT and the gene products required for efficient mobilization by PIL(W). MOB(W) plasmids could also be mobilized efficiently by PIL(N), the specific pilus of the IncN plasmid pCU1, but not by PIL(P), the specific pilus of the IncP plasmid RP1.